Novel Fluoroalkylated Surfactants in Soils Following Firefighting Foam Deployment During the Lac-Mégantic Railway Accident

Sequestration and potential release of PFAS from spent engineered sorbents

Per- and poly-fluoroalkyl substances (PFAS) have contaminated land and water at numerous sites worldwide that now require remediation. The most common approach for treating contaminated water currently relies on removal of PFAS by sorption. The spent sorbents loaded with PFAS can potentially be disposed of at landfills, provided the sorbed contaminants remain sequestered and certain risk criteria are met. Hence, it is essential that remediation sorbents (i) rapidly adsorb a large variety of PFAS under varying water chemistry conditions, and (ii) do not release the adsorbed PFAS in due course. This review aims at establishing the current state of knowledge about the potential release of PFAS that may occur during and after treatment. The scientific literature currently provides data for a very restricted range of long-chain PFAS. Our knowledge of the dynamics of PFAS adsorption processes on engineered sorbents is limited, and even less is known about their desorption processes. The sorption of PFAS can be strongly affected by changes in the solution pH, ionic strength and dissolved organic matter content, and the process is also subject to complex competition mechanisms in the presence of other PFAS as well as organic contaminants and inorganic salts. Several studies suggest that changes in one or several of these factors may trigger the release of PFAS from engineered sorbents. This phenomenon is more likely to occur for PFAS with shorter carbon chain lengths (<C8), at high pH and in the presence of other PFAS or other anionic sorbates. The release of PFAS from spent sorbent materials, stored or deposited under conditions that vary over time, is highly undesirable, as they can potentially become a secondary source of PFAS in the environment. Our analysis identifies a number of knowledge-gaps that should be urgently addressed in order to design sustainable remediation solutions, including an improved management of spent sorbent materials.

Software Comparison for Nontargeted Analysis of PFAS in AFFF-Contaminated Soil

Per- and polyfluoroalkyl substances (PFAS) are an emerging class of toxic environmental contaminants. Over 7500 PFAS exist, but reference standards are available for less than 2% of compounds. Nontargeted analysis using liquid chromatography-high-resolution tandem mass spectrometry is therefore an essential technique for increasing the analytical coverage of PFAS present in environmental samples. However, typical nontargeted data analysis is laborious and has a steep learning curve. Recently, FluoroMatch, a new open source, vendor neutral software, was published specifically for automating data processing for nontargeted analysis of PFAS and generating PFAS libraries. Here, we analyze soil contaminated with PFAS based aqueous film forming foam (AFFF) and compare the results produced by data analysis workflows using FluoroMatch and Compound Discoverer, an established nontargeted analysis program. High-confidence PFAS annotations were nearly identical between the methods, with 27 out of 32 compounds found using both Compound Discoverer and the modular version of FluoroMatch. Twenty-two high-confidence annotations were found using the comprehensive FluoroMatch Flow. The FluoroMatch method was faster and required significantly less manual curation than the Compound Discoverer method. Both platforms produced high-quality data that were useful for assessing PFAS contamination in the soil.

Evaluation of extraction workflows for quantitative analysis of per- and polyfluoroalkyl substances: A case study using soil adjacent to a landfill

Specific aspects of previously reported extraction workflows, for measurement of per- and polyfluoroalkyl substances (PFAS) in solid matrices, have not been adequately interrogated. The objective of this study was to explore the importance of each workflow step in providing the most appropriate extraction for a comprehensive set of PFAS (51 different species) in soil. We compared different procedures, including two pre-extraction set ups (overnight handling of samples prior to extraction), two extraction solvents (methanol (MeOH), and acetonitrile (ACN)), two extraction solvent volumes (10 mL and 8.5 mL), and two post-extraction cleanup strategies (ENVI-Carb and ion-pair). Of the 51 species targeted, 21 were at quantifiable levels in soil samples collected adjacent to a landfill, of which 13 PFAS were consistently detected among the different extraction workflows. Overall, results showed no significant difference in PFAS concentration between different extraction solvents and cleanup strategies. Perfluoropentanoic acid, perfluorohexanoic acid, and perfluorooctanoic acid had the highest concentrations in all extraction workflows, accounting for nearly 13%, 38%, and 17% of the total monitored PFAS (ΣPFAS), respectively. While final concentration values were similar across methods, recovery and accuracy studies showed that MeOH had the best recovery, with 88% of the isotopically labeled PFAS standards showing extraction recovery within the acceptable range of 80% to 120% (compared to 14% of isotopically labeled PFAS standards in workflows using ACN). Upon examination of additional cleanup steps, 67% of monitored PFAS (out of 51 total PFAS monitored), on average, exhibited higher accuracy (relative error ≤20%) using ENVI-Carb clean up (in comparison with 51% in workflows using ion pair clean up). Results also demonstrated that larger volumes of MeOH (and subsequent re-extractions) did not yield a better recovery, enabling a reduction in overall analysis time and cost in comparison to many published methods.

PFAS soil and groundwater contamination via industrial airborne emission and land deposition in SW Vermont and Eastern New York State, USA

In order to understand the extent to which airborne PFAS emission can impact soil and groundwater, we conducted a sampling campaign in areas of conserved forest lands near Bennington, VT/Hoosick Falls, NY. This has been home to sources of PFAS air-emissions from Teflon-coating operations for over 50 years. Since 2015, the Vermont and New York Departments of Environmental Conservation have documented ∼1200 residential wells and two municipal water systems across a 200 km2 area contaminated with perfluorooctanoic acid (PFOA). Given the large areal extent of the plume, and the fact that much of the contaminated area lies up-gradient and across rivers from manufactures, we seek to determine if groundwater contamination could have resulted primarily from air-emission, land deposition, and subsequent leaching to infiltrating groundwater. Sampling of soils and groundwater in the Green Mountain National Forest (GMNF) downwind of factories shows that both soil and groundwater PFOA contamination extend uninterrupted from inhabited areas into conserved forest lands. Groundwater springs and seeps in the GMNF located 8 km downwind, but >300 meters vertically above factories, contain up to 100 ppt PFOA. Our results indicate that air-emitted PFAS can contaminate groundwater and soil in areas outside of those normally considered down-gradient of a source with respect to regional groundwater flow.

Biotransformation of perfluoroalkyl acid precursors from various environmental systems: advances and perspectives

Perfluoroalkyl acids (PFAAs) are widely used in industrial production and daily life because of their unique physicochemical properties, such as their hydrophobicity, oleophobicity, surface activity, and thermal stability. Perfluorosulfonic acids (PFSAs) and perfluorocarboxylic acids (PFCAs) are the most studied PFAAs due to their global occurrence. PFAAs are environmentally persistent, toxic, and the long-chain homologs are also bioaccumulative. Exposure to PFAAs may arise directly from emission or indirectly via the environmental release and degradation of PFAA precursors. Precursors themselves or their conversion intermediates can present deleterious effects, including hepatotoxicity, reproductive toxicity, developmental toxicity, and genetic toxicity. Therefore, exposure to PFAA precursors constitutes a potential hazard for environmental contamination. In order to comprehensively evaluate the environmental fate and effects of PFAA precursors and their connection with PFSAs and PFCAs, we review environmental biodegradability studies carried out with microbial strains, activated sludge, plants, and earthworms over the past decade. In particular, we review perfluorooctyl-sulfonamide-based precursors, including perfluroooctane sulfonamide (FOSA) and its N-ethyl derivative (EtFOSA), N-ethyl perfluorooctane sulfonamido ethanol (EtFOSE), and EtFOSE-based phosphate diester (DiSAmPAP). Fluorotelomerization-based precursors are also reviewed, including fluorotelomer alcohols (FTOH), fluorotelomer sulfonates (FTSA), and a suite of their transformation products. Though limited information is currently available on zwitterionic PFAS precursors, a preliminary review of data available for 6:2 fluorotelomer sulfonamide betaine (FTAB) was also conducted. Furthermore, we update and refine the recent knowledge on biotransformation strategies with a focus on metabolic pathways and mechanisms involved in the biotransformation of PFAA precursors. The biotransformation of PFAA precursors mainly involves the cleavage of carbon-fluorine (C-F) bonds and the degradation of non-fluorinated functional groups via oxidation, dealkylation, and defluorination to form shorter-chained PFAAs. Based on the existing research, the current problems and future research directions on the biotransformation of PFAA precursors are proposed.

Target, Nontarget, and Suspect Screening and Temporal Trends of Per- and Polyfluoroalkyl Substances in Marine Mammals from the South China Sea

Per- and polyfluoroalkyl substances (PFASs) have been manufactured and widely used for over 60 years. Currently, there are thousands of marketed PFASs, but only dozens of them are routinely monitored. This work involved target, nontarget, and suspect screening of PFASs in the liver of Indo-Pacific humpback dolphin (Sousa chinensis) and finless porpoise (Neophocaena phocaenoides), two resident marine mammals in the South China Sea, stranded between 2012 and 2018. Among the 21 target PFASs, perfluorooctane sulfonate and 6:2 chlorinated polyfluoroalkyl ether sulfonate (6:2 Cl-PFESA) predominated in the samples, accounting for 46 and 30% of the total PFASs, respectively. Significantly higher total target PFAS concentrations (p < 0.05) were found in dolphin liver samples [3.23 × 10³ ± 2.63 × 10³ ng/g dry weight (dw)] than in porpoise liver samples (2.63 × 10³ ± 1.10 × 10³ ng/g dw). Significant increasing temporal trends (p < 0.05) were found in the concentrations of two emerging PFASs, perfluoroethylcyclohexane sulfonate and 2,3,3,3-tetrafluoro-2-propanoate in porpoises, indicating increasing pollution by these emerging PFASs. Forty-four PFASs from 9 classes were additionally identified by nontarget and suspect screening, among which 15 compounds were reported for the first time in marine mammals. A primary risk assessment showed that the emerging PFAS 6:2 Cl-PFESA could have possible adverse effects in terms of reproductive injury potential on most of the investigated cetaceans.

Reconstructing the Composition of Per- and Polyfluoroalkyl Substances in Contemporary Aqueous Film-Forming Foams

Hundreds of public water systems across the United States have been contaminated by the use of aqueous film-forming foams (AFFF) containing per- and polyfluoroalkyl substances (PFAS) during firefighting and training activities. Prior work shows AFFF contain hundreds of polyfluoroalkyl precursors missed by standard methods. However, the most abundant precursors in AFFF remain uncertain, and mixture contents are confidential business information, hindering proactive management of PFAS exposure risks. Here, we develop and apply a novel method (Bayesian inference) for reconstructing the fluorinated chain lengths, manufacturing origin, and concentrations of oxidizable precursors obtained from the total oxidizable precursor (TOP) assay that is generally applicable to all aqueous samples. Results show virtually all (median 104 ± 19%) extractable organofluorine (EOF) in contemporary and legacy AFFF consists of targeted compounds and oxidizable precursors, 90% of which are 6:2 fluorotelomers in contemporary products. Using high-resolution mass spectrometry, we further resolved the 6:2 fluorotelomers to assign the identity of 14 major compounds, yielding a priority list that accounts for almost all detectable PFAS in contemporary AFFF. This combination of methods can accurately assign the total PFAS mass attributable to AFFF in any aqueous sample with differentiation of gross precursor classes and identification of major precursor species.

Spatial Trends of Anionic, Zwitterionic, and Cationic PFASs at an AFFF-Impacted Site

Soil and groundwater from an aqueous film-forming foam (AFFF)-impacted site were sampled at high resolution (n = 105 for soil, n = 58 for groundwater) and analyzed for an extensive list of anionic, zwitterionic, and cationic poly- and perfluoroalkyl substances (PFASs). Spatial trends for perfluoroalkyl acids and many precursors enabled a better understanding of PFAS composition, transport, and transformation. All PFASs without analytical standards were semi-quantified. Summed PFAS and individual PFAS concentrations were often higher at depth than near the surface in soil and groundwater. Zwitterionic and cationic compounds composed a majority of the total PFAS mass (up to 97%) in firefighter training area (FTA) soil. Composition of PFAS class, chain length, and structural isomers changed with depth and distance from the FTA, suggesting in situ transformation and differential transport. The percentage of branched perfluorooctane sulfonate increased with depth, consistent with differential isomeric transport. However, linear perfluorooctanoic acid (PFOA) was enriched, suggesting fluorotelomer precursor transformation to linear PFOA. Perfluorohexane sulfonamide, a potential transformation product of sulfonamide-based PFASs, was present at high concentrations (maximum 448 ng/g in soil, 3.4 mg/L in groundwater). Precursor compounds may create long-term sources of perfluoroalkyl acids, although many pathways remain unknown; precursor analysis is critical for PFAS fate and transport understanding.

Per- and polyfluoroalkyl substances (PFASs) in contaminated coastal marine waters of the Saudi Arabian Red Sea: a baseline study

Per- and polyfluoroalkyl substances (PFASs) are today considered important constituents of the continuously growing substance group of persistent contaminants of emerging environmental concern (PCEC). Here, we report for the first time the concentrations of 12 relevant PFASs in 28 marine water samples from the Saudi Arabian coastal waters of the Red Sea. The sum levels of 12 PFASs (Σ₁₂ PFAS) in surface seawater ranged from <LOQ to 956 ngL^-1. For the reference background site of this study, Σ₁₂ PFAS levels ranged from <LOQ to 10.9 ng/L. The highest PFAS levels have been found in Al-Arbaeen and Al-Shabab, two lagoons continuously receiving treated sewage effluents. PFHxA, PFHxS, and 6:2 FTS were the most prevalent PFASs with relatively high concentrations. Discharge of municipal and industrial wastewaters is considered an important source of PFASs. The pattern of PFASs observed here suggests that the usage of PFAS-containing aqueous film-forming foams (AFFFs) is a potential additional source for these compounds in Al-Arbaeen and Al-Shabab lagoons. However, a systematic elucidation of local PFASs sources is needed. Contamination of the Red Sea waters with PFASs poses a potential imminent risk to the marine environment of the Red Sea and ultimately may even affect the health of human consumers through the consumption of local seafood.

Occurrence and Distribution of Per- and Polyfluoroalkyl Substances in Tianjin, China: The Contribution of Emerging and Unknown Analogues

Tianjin, located in Bohai Bay, China, constitutes a relevant study area to investigate emerging per- and polyfluoroalkyl substances (PFASs) due to its high population density, clustering of chemical and aircraft industries, as well as international airports, harbors, and oil rigs. In this study, 53 anionic, zwitterionic, and cationic PFASs were monitored in river surface water, groundwater, seawater, and sediments in this area (overall n = 226). 6:2 chlorinated polyfluorinated ether sulfonic acid (Cl-PFESA), perfluorooctanoic acid, and perfluorooctane sulfonic acid were generally the predominant PFASs. 6:2 fluorotelomer sulfonamidoalkyl betaine (6:2 FTAB) was also widespread (occurrence >86%), with the highest concentration (1300 ng/L) detected at contamination hot spots impacted by wastewater effluents. The aqueous film-forming foam (AFFF)-related PFASs with sulfonamide betaine, amine oxide, amine, or quaternary ammonium moieties are also reported for the first time in river water and seawater samples. Fifteen classes of infrequently reported PFASs, including n:2 FTABs and n:2 fluorotelomer sulfonamide amines, hydrogen-substituted PFESA homologues, and p-perfluorous nonenoxybenzenesulfonate (OBS), were also identified in the water and sediment samples using suspect screening. Field-derived sediment-water distribution coefficients (K_d) of these emerging PFASs are provided for the first time, confirming that cationic and zwitterionic PFASs tend to be strongly associated with sediments.

A Review of the Applications, Environmental Release, and Remediation Technologies of Per- and Polyfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFAS) are pollutants that have demonstrated a high level of environmental persistence and are very difficult to remediate. As the body of literature on their environmental effects has increased, so has regulatory and research scrutiny. The widespread usage of PFAS in industrial applications and consumer products, complicated by their environmental release, mobility, fate, and transport, have resulted in multiple exposure routes for humans. Furthermore, low screening levels and stringent regulatory standards that vary by state introduce considerable uncertainty and potential costs in the environmental management of PFAS. The recalcitrant nature of PFAS render their removal difficult, but existing and emerging technologies can be leveraged to destroy or sequester PFAS in a variety of environmental matrices. Additionally, new research on PFAS remediation technologies has emerged to address the efficiency, costs, and other shortcomings of existing remediation methods. Further research on the impact of field parameters such as secondary water quality effects, the presence of co-contaminants and emerging PFAS, reaction mechanisms, defluorination yields, and the decomposition products of treatment technologies is needed to fully evaluate these emerging technologies, and industry attention should focus on treatment train approaches to improve efficiency and reduce the cost of treatment.

PFAS concentrations in soils: Background levels versus contaminated sites

Per- and polyfluoroalkyl substances (PFAS) are contaminants of critical concern due to their persistence, widespread distribution in the environment, and potential human-health impacts. In this work, published studies of PFAS concentrations in soils were compiled from the literature. These data were combined with results obtained from a large curated database of PFAS soil concentrations for contaminated sites. In aggregate, the compiled data set comprises >30,000 samples collected from >2500 sites distributed throughout the world. Data were collected for three types of sites- background sites, primary-source sites (fire-training areas, manufacturing plants), and secondary-source sites (biosolids application, irrigation water use). The aggregated soil-survey reports comprise samples collected from all continents, and from a large variety of locations in both urban and rural regions. PFAS were present in soil at almost every site tested. Low but measurable concentrations were observed even in remote regions far from potential PFOS sources. Concentrations reported for PFAS-contaminated sites were generally orders-of-magnitude greater than background levels, particularly for PFOS. Maximum reported PFOS concentrations ranged upwards of several hundred mg/kg. Analysis of depth profiles indicates significant retention of PFAS in the vadose zone over decadal timeframes and the occurrence of leaching to groundwater. It is noteworthy that soil concentrations reported for PFAS at contaminated sites are often orders-of-magnitude higher than typical groundwater concentrations. The results of this study demonstrate that PFAS are present in soils across the globe, and indicate that soil is a significant reservoir for PFAS. A critical question of concern is the long-term migration potential to surface water, groundwater, and the atmosphere. This warrants increased focus on the transport and fate behavior of PFAS in soil and the vadose zone, in regards to both research and site investigations.

β-Cyclodextrin Polymers with Different Cross-Linkers and Ion-Exchange Resins Exhibit Variable Adsorption of Anionic, Zwitterionic, and Nonionic PFASs

Per- and polyfluoroalkyl substances (PFASs) occur in groundwater as mixtures of anionic, cationic, zwitterionic, and nonionic species, although few remediation technologies have been evaluated to assess the removal of different types of PFASs. In this study, we evaluated the performance of three β-cyclodextrin polymers (CDPs), an anion-exchange (AE) resin, and a cation-exchange (CE) resin for the removal of anionic, zwitterionic, and nonionic PFASs from water. We found that a CDP with a negative surface charge rapidly removes all zwitterionic PFASs with log K_D values ranging between 2.4 and 3.1, and the CE resin rapidly removes two zwitterionic PFASs with log K_D values of 1.8 and 1.9. The CDPs with a positive surface charge rapidly remove all anionic PFASs with log K_D values between 2.7 and 4.1, and the AE resin removes all anionic PFASs relatively slowly with log K_D values between 2.0 and 2.3. All adsorbents exhibited variable removal of the nonionic PFASs and some adsorption inhibition at higher pH values and in the presence of groundwater matrix constituents. Our findings provide insight into how adsorbents can be combined to remediate groundwater contaminated with complex mixtures of different types of PFASs.

Temporal and spatial analysis of per and polyfluoroalkyl substances in surface waters of Houston ship channel following a large-scale industrial fire incident

Firefighting foams contain per- and polyfluoroalkyl substances (PFAS) - a class of compounds widely used as surfactants. PFAS are persistent organic pollutants that have been reported in waterways and drinking water systems across the United States. These substances are of interest to both regulatory agencies and the general public because of their persistence in the environment and association with adverse health effects. PFAS can be released in large quantities during industrial incidents because they are present in most firefighting foams used to suppress chemical fires; however, little is known about persistence of PFAS in public waterways after such events. In response to large-scale fires at Intercontinental Terminal Company (ITC) in Houston, Texas in March 2019, almost 5 million liters of class B firefighting foams were used. Much of this material flowed into the Houston Ship Channel and Galveston Bay (HSC/GB) and concerns were raised about the levels of PFAS in these water bodies that have commercial and recreational uses. To evaluate the impact of the ITC incident response on PFAS levels in HSC/GB, we collected 52 surface water samples from 12 locations over a 6-month period after the incident. Samples were analyzed using liquid chromatography-mass spectrometry to evaluate 27 PFAS, including perfluorocarboxylic acids, perfluorosulfonates and fluorotelomers. Among PFAS that were evaluated, 6:2 FTS and PFOS were detected at highest concentrations. Temporal and spatial profiles of PFAS were established; we found a major peak in the level of many PFAS in the days and weeks after the incident and a gradual decline over several months with patterns consistent with the tide- and wave-associated water movements. This work documents the impact of a large-scale industrial fire, on the environmental levels of PFAS, establishes a baseline concentration of PFAS in HSC/GB, and highlights the critical need for development of PFAS water quality standards.

Molecular mechanisms of per- and polyfluoroalkyl substances on a modified clay: a combined experimental and molecular simulation study

Repeated application of aqueous film-forming foams (AFFF) in designated firefighting training areas has caused severe groundwater contamination by per- and polyfluoroalkyl substances (PFASs). Many research efforts are currently engaged for the effective removal of these chemicals from environmental waters. In this study, we demonstrate that modified clay produced by intercalating quaternary ammonium cations in the exchangeable interlayer sites of smectite clay can effectively remove PFAS pollutants in real groundwater via strong adsorption. The performance of the modified clay (with removal efficiencies 95~99%) is superior to those of granular activated carbon or hard-wood biochar and comparable to an ion exchange resin. Removal efficiency is not impacted by potential organic co-contaminants (e.g., diesel, BTEX, TCE, and 1,4 dioxane) or water chemistry (Ca²⁺ and Na⁺) at environmentally relevant concentrations. Furthermore, piecewise isotherms are identified to represent the uptake of PFASs by the modified clay. Based on molecular dynamics simulations, the anionic PFASs first occupy the highly polarized bare interlayer edge sites leading to a linear isotherm and then the interlayer surface sites resulting in a Langmuir isotherm. The ionic interactions between the cationic intercalant (N⁺) and the terminal oxygen atoms of carboxylate or sulfonate groups of PFASs play a dominant role in adsorption, and the lateral interaction in particular fluorophilic attraction among PFASs accelerate the adsorption. The strength of these interactions is quantified using Density Functional Theory calculations. Simulation results match reasonably well with the experimentally determined basal spacing and Fourier transform infrared spectroscopy of the modified clay loaded with PFASs. Overall, the combined experimental and molecular simulation studies elucidate the adsorption mechanism of PFASs on the modified clay and provide critical information to guide the use of modified clays for PFAS water treatment in the field.

Emerging and legacy per- and polyfluoroalkyl substances in water, sediment, and air of the Bohai Sea and its surrounding rivers

Per- and polyfluoroalkyl substances (PFASs) contamination in the Bohai Sea and its surrounding rivers has attracted considerable attention in recent years. However, few studies have been conducted regarding the distribution of PFASs in multiple environmental media and their distributions between the suspended particles and dissolved phases. In this study, surface water, surface sediment, and air samples were collected at the Bohai Sea to investigate the concentration and distribution of 39 targeted PFASs. Moreover, river water samples from 35 river estuaries were collected to estimate PFAS discharge fluxes to the Bohai Sea. The results showed that total ionic compound (Σi-PFASs) concentrations ranged from 19.3 to 967 ng/L (mean 125 ± 152 ng/L) in the water and 0.70-4.13 ng/g dw (1.78 ± 0.76 ng/g) in surface sediment of the Bohai Sea, respectively. In the estuaries, Σi-PFAS concentrations were ranged from 10.5 to 13500 ng/L (882 ± 2410 ng/L). In the air, ΣPFAS (Σi-PFASs + Σn-PFASs) concentrations ranged from 199 to 678 pg/m³ (462 ± 166 pg/m³). Perfluorooctanoic acid (PFOA) was the predominant compound in the seawater, sediment, and river water; in the air, 8:2 fluorotelomer alcohol was predominant. Xiaoqing River discharged the largest Σi-PFAS flux to the Bohai Sea, which was estimated as 12,100 kg/y. Some alternatives, i.e., 6:2 fluorotelomer sulfonate acid (6:2 FTSA), hexafluoropropylene oxide dimer acid (HFPO-DA), and chlorinated 6:2 polyfluorinated ether sulfonic acid (Cl-6:2 PFESA), showed higher levels than or comparable concentrations to those of the C8 legacy PFASs in some sampling sites. The particle-derived distribution coefficient in seawater was higher than that in the river water. Using high resolution mass spectrometry, 29 nontarget emerging PFASs were found in 3 river water and 3 seawater samples. Further studies should be conducted to clarify the sources and ecotoxicological effects of these emerging PFASs in the Bohai Sea area.

In Vivo Generation of PFOA, PFOS, and Other Compounds from Cationic and Zwitterionic Per- and Polyfluoroalkyl Substances in a Terrestrial Invertebrate (Lumbricus terrestris)

Perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) are two environmentally persistent per- and polyfluoroalkyl substances (PFAS) that have been detected globally in human tissues and fluids. As part of a project investigating the indirect sources of PFOA/PFOS in the environment and engineered systems, this study is concerned with the mechanisms leading to their in vivo generation in terrestrial invertebrates. We demonstrate here the formation of PFOA and PFOS in earthworms (Lumbricus terrestris) from a group of four zwitterionic/cationic polyfluoroalkyl amides and sulfonamides. In bioaccumulation tests, the zwitterionic PFAS compounds were metabolized within 10 days to PFOA/PFOS at yields of 3.4-20.8 mol % by day 21 and several infrequently reported PFAS species for which chemical structures were determined using high-resolution mass spectrometry. Cationic PFAS, on the other hand, were found to be much less metabolizable in terms of the number (n = 2) and yields (0.9-5.1 mol %) of metabolites. Peak-shaped bioaccumulation profiles were frequently observed for the studied PFAS. Residual zwitterionic/cationic PFAS in earthworms were detected at the end of the elimination phase, indicating that not all zwitterionic/cationic PFAS molecules in vivo are available for enzymatic degradation. Finally, the relative importance of different exposure routes (i.e., waterborne and dietary exposure) was investigated.

Enhanced Extraction of AFFF-Associated PFASs from Source Zone Soils

Poly- and perfluoroalkyl substances (PFASs) derived from aqueous film-forming foam (AFFF) are increasingly recognized as groundwater contaminants, though the composition and distribution of AFFF-derived PFASs associated with soils and subsurface sediments remain largely unknown. This is particularly true for zwitterionic and cationic PFASs, which may be incompletely extracted from subsurface solids by analytical methods developed for anionic PFASs. Therefore, a method involving sequential basic and acidic methanol extractions was developed and evaluated for recovery of anionic, cationic, and zwitterionic PFASs from field-collected, AFFF-impacted soils. The method was validated by spike-recovery experiments with equilibrated soil-water-AFFF and analytical standards. To determine the relative importance of PFASs lacking commercially available analytical standards, their concentrations were estimated by a novel semiquantitation approach. Total PFAS concentrations determined by semiquantitation were compared with concentrations determined by the total oxidizable precursor assay. Finally, the described method was applied to two soil cores from former fire-training areas in which cations and zwitterions were found to contribute up to 97% of the total PFAS mass. This result demonstrates the need for extraction and analysis methods, such as the ones presented here, that are capable of quantifying cationic and zwitterionic PFASs in AFFF-impacted source zone soils.

Fluorine Mass Balance and Suspect Screening in Marine Mammals from the Northern Hemisphere

There is increasing evidence that the ∼20 routinely monitored perfluoroalkyl and polyfluoroalkyl substances (PFASs) account for only a fraction of extractable organofluorine (EOF) occurring in the environment. To assess whether PFAS exposure is being underestimated in marine mammals from the Northern Hemisphere, we performed a fluorine mass balance on liver tissues from 11 different species using a combination of targeted PFAS analysis, EOF and total fluorine determination, and suspect screening. Samples were obtained from the east coast United States (US), west and east coast of Greenland, Iceland, and Sweden from 2000 to 2017. Of the 36 target PFASs, perfluorooctane sulfonate (PFOS) dominated in all but one Icelandic and three US samples, where the 7:3 fluorotelomer carboxylic acid (7:3 FTCA) was prevalent. This is the first report of 7:3 FTCA in polar bears (∼1000 ng/g, ww) and cetaceans (<6-190 ng/g, ww). In 18 out of 25 samples, EOF was not significantly greater than fluorine concentrations derived from sum target PFASs. For the remaining 7 samples (mostly from the US east coast), 30-75% of the EOF was unidentified. Suspect screening revealed an additional 37 PFASs (not included in the targeted analysis) bringing the total to 63 detected PFASs from 12 different classes. Overall, these results highlight the importance of a multiplatform approach for accurately characterizing PFAS exposure in marine mammals.

Fluorine Mass Balance and Suspect Screening in Marine Mammals from the Northern Hemisphere

There is increasing evidence that the ∼20 routinely monitored perfluoroalkyl and polyfluoroalkyl substances (PFASs) account for only a fraction of extractable organofluorine (EOF) occurring in the environment. To assess whether PFAS exposure is being underestimated in marine mammals from the Northern Hemisphere, we performed a fluorine mass balance on liver tissues from 11 different species using a combination of targeted PFAS analysis, EOF and total fluorine determination, and suspect screening. Samples were obtained from the east coast United States (US), west and east coast of Greenland, Iceland, and Sweden from 2000 to 2017. Of the 36 target PFASs, perfluorooctane sulfonate (PFOS) dominated in all but one Icelandic and three US samples, where the 7:3 fluorotelomer carboxylic acid (7:3 FTCA) was prevalent. This is the first report of 7:3 FTCA in polar bears (∼1000 ng/g, ww) and cetaceans (<6-190 ng/g, ww). In 18 out of 25 samples, EOF was not significantly greater than fluorine concentrations derived from sum target PFASs. For the remaining 7 samples (mostly from the US east coast), 30-75% of the EOF was unidentified. Suspect screening revealed an additional 37 PFASs (not included in the targeted analysis) bringing the total to 63 detected PFASs from 12 different classes. Overall, these results highlight the importance of a multiplatform approach for accurately characterizing PFAS exposure in marine mammals.

Transformation of 6:2 Fluorotelomer Sulfonate by Cobalt(II)-Activated Peroxymonosulfate

Peroxymonosulfate (PMS)-based advanced oxidation processes generate highly reactive SO₄^•- and are promising for water treatment. In this study, we investigated the reaction mechanism of 6:2 fluorotelomer sulfonate (6:2 FTS) with Co²⁺-activated PMS. 6:2 FTS was simultaneously transformed to perfluoroalkyl carboxylic acids (C2-C7 PFCAs) of different chain lengths, with perfluorohexanoic acid (C6) as the predominant one. The mass balance of the intermediates and products versus the initially added 6:2 FTS was close to 100% over the reaction period. Using chemical scavenging methods, we identified that ^•OH, instead of SO₄^•-, was the oxidant initiating the reaction of 6:2 FTS. ^•OH was mainly produced from SO₄^•- reacting with H₂O. Thus, the reactivity of 6:2 FTS was controlled by the factors affecting the production and scavenging of both SO₄^•- and ^•OH. Density functional theory calculations showed that ^•OH oxidizes 6:2 FTS by H-abstraction from ethyl carbons. This is the first study that demonstrates that ^•OH in Co²⁺-activated PMS can play a significant role in contaminant transformations. The results indicate that great caution should be taken when PMS or other agents that generate ^•OH are used for the treatment of water containing 6:2 FTS or its structural analogs.

Sorption of Polyfluoroalkyl Surfactants on Surface Soils: Effect of Molecular Structures, Soil Properties, and Solution Chemistry

Zwitterionic, cationic, and anionic per- and polyfluoroalkyl substances (PFASs) are identified in aqueous film-forming foam (AFFF) concentrates and AFFF-impacted sites. However, the mobility potential of zwitterionic and cationic PFASs is poorly understood, preventing reliable site assessment. The study aimed to elucidate the mobility behaviors of PFASs of various charge states in saturated soil-water systems and assess critical influencing factors. Five anionic, three zwitterionic, and one cationic PFASs were investigated in five soils through batch sorption experiments. Pairwise comparison revealed that the quaternary ammonium group imparted a strong affinity of cationic perfluorooctaneamide ammonium compound (PFOAAmS) for soils. The influence of the quaternary ammonium group is mitigated in polyfluoroalkyl betaines, yet perfluorooctane sulfonamidoalkyl betaine (PFOSB) showed strong sorption in selected soils. Two soil bulk properties showed some correlations with the soil-water distribution coefficient (K_d). A positive correlation with the fraction of soil organic carbon was found only for anionic PFASs, whereas cation exchange capacity had an approximate positive correlation with K_d only for PFOAAmS. Water chemistry (Ca²⁺ and pH) influences the sorption of nonanionic PFASs in very distinct fashions or even in opposite trends to what was known for anionic PFASs. Sorption was insensitive to pH changes except for PFOSB; PFOSB underwent profound sorption reduction because its speciation occurs around neutral pH, while the two other betaines and PFOAAmS have pK_a values that are outside of the environmentally relevant range. The lack of correlations suggests that the transport potential of PFASs is probably highly site-specific. It remains a challenge in deciphering PFAS sorption mechanisms and predicting how AFFF plumes migrate.

Bioaccumulation of Zwitterionic Polyfluoroalkyl Substances in Earthworms Exposed to Aqueous Film-Forming Foam Impacted Soils

Critical knowledge gaps remain regarding the fate and effects of zwitterionic, cationic, and anionic perfluoroalkyl and polyfluoroalkyl substances (PFASs), including assessment of their bioaccumulation potential. Here, biota soil accumulation factors (BSAFs) were assessed in earthworms (Eisenia fetida) exposed to soil microcosms amended with zwitterionic fluorotelomers and anionic perfluoroalkyl acids. The 6:2 fluorotelomer sulfonamidoalkyl betaine (6:2 FTAB) bioaccumulated in earthworms [BSAF ∼ 2.5-5.4 (g_dw,worm/g_dw,soil)^-1] but to a lesser extent than perfluorooctane sulfonate (PFOS: BSAF ∼ 21-29). The BSAF of perfluorocarboxylates increased from ∼2.0 for C₄-C₆ analogues to ∼92 for perfluorotridecanoate (C₁₃). In earthworms exposed to Ansulite and Arctic Foam aqueous film-forming foams (AFFFs), the BSAF was related to perfluorinated chain length for n:3 fluorotelomer betaines (FtBs), n:1:2 FtB, and n:2 FTAB. Earthworms were also collected in situ from a fire-equipment testing site at a major Canadian airport. Summed PFAS concentrations were between 65 000 and 830 000 ng g^-1 wet weight, possibly the highest burden recorded in terrestrial biota. Fluorotelomer sulfonates (6:2 FTS, 8:2 FTS, and 10:2 FTS) and FtB were particularly prevalent. Field worms also displayed elevated concentrations of n:3 acids (n = 3-11), but not those from laboratory microcosms exposed to fluorotelomer-based AFFFs. The findings provide an important confirmation to recent data suggesting that fluorotelomer compounds may accumulate in invertebrate species with limited metabolization.

Characterization of the Chemical Contents of Fluorinated and Fluorine-Free Firefighting Foams Using a Novel Workflow Combining Nontarget Screening and Total Fluorine Analysis

Aqueous film-forming foams (AFFFs) are widely used to extinguish liquid fires due to their film-forming properties. AFFF formulation historically contains per- and polyfluoroalkyl substances (PFASs) that can be very persistent and pose a health risk to biota and humans. Detailed analysis of the chemical composition of AFFFs can provide a better understanding on the potential environmental impact of the ingredients. In this study, a novel workflow combining target analysis, nontarget screening analysis (NTA), total fluorine (TF) analysis, and inorganic fluoride (IF) analysis was applied to disclose the chemical composition of 24 foams intended for liquid fires. Foams marketed as containing PFASs as well as fluorine-free foams were included. By comparing the sum of targeted PFASs and total organofluorine concentrations, a mass balance of known and unknown organofluorine could be calculated. Known organofluorine accounted for <1% in most fluorine-containing AFFFs, and it was confirmed that the foams marketed as fluorine-free did not contain measurable amounts of organofluorine substances. Five fluorinated substances were tentatively identified, and non-fluorinated zwitterionic betaine compounds, which are considered to be replacement substances for PFASs, were tentatively identified in the organofluorine-free foams.

A new method to search for per- and polyfluoroalkyl substances (PFASs) by linking fragmentation flags with their molecular ions by drift time using ion mobility spectrometry

Per- and polyfluoroalkyl substances (PFASs) are a group of anthropogenic organic fluorinated compounds that have been detected widely. To discover unknown PFASs, previous researchers have applied high-resolution mass spectrometer using fragmentation flagging approach with common fragment ion at the same retention time as the flags. However, it was difficult to search for their molecular ion from co-eluting peaks in the full-scan spectrum at a specific retention time. Here, we attempted to utilize drift time acquired by ion mobility spectrometry for making linkages between fragment ions and their molecular ions. For validating the process, standard solution spiked with PFASs were analyzed by liquid chromatography/ion mobility - quadrupole time-of-flight mass spectrometry (LC/IM-QTOF-MS). Fluorinated fragment ions (fragmentation flags) were categorized into three classes: Class 1 (120 types of [C_xF_y]^-), Class 2 (123 types of [C_xF_yO]^-), Class 3 (131 types of [C_xF_yO₃S]^-) and all overlapping fragmentation flags detected at an identical retention time were bundled together as a "flag set". Injecting standard mixed solution of 20 types of PFASs resulted in picking up 20 flag sets by fragmentation flagging. All the fragmentation flags were detected within a designated range of drift time, and their molecular ion was confirmed as a PFAS spiked in the standard solution even when co-eluting compounds were found at almost same retention time. This method was applied to a household fire extinguisher liquid, resulting in finding out nine molecular ions. Therefore, the new linking method achieved rapid searching for the prospective molecular ions using LC/IM-QTOF-MS.

Sorption and Desorption Mechanisms of Cationic and Zwitterionic Per- and Polyfluoroalkyl Substances in Natural Soils: Thermodynamics and Hysteresis

Sorption linearity and reversibility are implicit in models for the fate and transport of per- and polyfluoroalkyl substances (PFAS). In this study, however, we found that the sorption of cationic and zwitterionic PFAS in natural soils was highly nonlinear. The nonlinearity was so severe that it led to a variation in the coefficient of sorption by several orders of magnitude over the experimental concentration range. This implies a considerable increase in sorption as concentration falls in the natural environment. Sorption of cationic PFAS correlated strongly with the soil organic matter (SOM) content and was reversible in all soils. Sorption of zwitterionic PFAS, on the other hand, displayed concentration-dependent hysteresis in soils with a low SOM content. The irreversibility, which was associated with neither SOM, pore deformation, nor surface complexation, was likely caused by the entrapment of molecules in porous structures within inorganic components of soil aggregates. Furthermore, electrostatic interactions with negatively charged soil constituents and the hydrophobic effect were found to be major sorption driving forces for cationic/zwitterionic PFAS at low and high concentrations, respectively. The maximum electrostatic potential of PFAS ions, computed using density functional theory, was found to be a useful predictor of the sorption of ionic PFAS species.

New Insights into the Degradation Mechanism of Perfluorooctanoic Acid by Persulfate from Density Functional Theory and Experimental Data

Thermally activated persulfate is a promising oxidant for in situ remediation of perfluorooctanoic acid (PFOA), yet a comprehensive understanding of the degradation mechanism is still lacking. In this study, we used density functional theory (DFT) calculations and experimental data to map entire reaction pathways for the degradation of PFOA by persulfate, with specific considerations on the influence of pH. The DFT results showed that the rate-limiting step was the first electron abstraction from PFOA, yet the generation of SO₄^•- from the decomposition of persulfate contributed a large part of the free energy of activation (ΔG^‡) for the overall reaction. The subsequent steps did not contribute to the ΔG^‡. For the electron abstraction from PFOA, we investigated reactions using protonated and deprotonated species of PFOA and SO₄^•- and showed that the reaction of anionic PFOA with HSO₄^• was most favorable with a ΔG^‡ of 7.2 kJ/mol. This explains why low pH (<3.5) is a sine qua non condition for the degradation of PFOA by persulfate. The overall ΔG^‡ derived theoretically based on the pathway involved HSO₄^• was consistent with the ΔG^‡ determined experimentally. This study provides valuable insight into remediation strategies that include persulfate as an oxidizing agent for perfluoroalkyl carboxylic acids.

Transformation of novel polyfluoroalkyl substances (PFASs) as co-contaminants during biopile remediation of petroleum hydrocarbons

Aqueous film forming foams (AFFFs) containing perfluoroalkyl and polyfluoroalkyl substances (PFASs) are commonly deployed to extinguish hydrocarbon fuel fires, resulting in petroleum hydrocarbons coexisting with PFASs in contaminated soil. Nutrient-amended and aerated biopiles used for petroleum hydrocarbon bioremediation could cause unintended transformation of polyfluorinated substances into perfluoroalkyl carboxylates (PFCAs). The study sought to examine environmental behaviors of PFASs in engineered treatment facilities by monitoring AFFF-derived PFASs under three nutrient conditions. The influence of nutrient levels on degradation kinetics and efficiency was found to vary between the two chemical classes and among individual PFASs. A high number of compounds including the zwitterionic polyfluoroalkyl betaines that have aged in the field for two years were continuously biotransforming in lab reactors, demonstrating their slow kinetics and environmental persistence. The low yield to PFCAs implies that the processes such as the formation of bound residues or irreversible sorption might play a major role in reducing detectable levels of zwitterionic PFASs. The high persistence of betaines was further confirmed by the behaviors of a freshly spiked sulfonamide betaine. The study demonstrated complex chemical dynamics in AFFF-impacted soils and the challenges for predicting the fate of PFASs in soil biopiling facilities.

Degradation and defluorination of 6:2 fluorotelomer sulfonamidoalkyl betaine and 6:2 fluorotelomer sulfonate by Gordonia sp. strain NB4-1Y under sulfur-limiting conditions

6:2 fluorotelomer sulfonamidoalkyl betaine (6:2 FTAB) is a major component of aqueous film-forming foams (AFFFs) used for firefighting and is frequently detected, along with one of its suspected transformation products, 6:2 fluorotelomer sulfonate (6:2 FTSA), in terrestrial and aquatic ecosystems impacted by AFFF usage. Biochemical processes underlying bacterial biodegradation of these compounds remain poorly understood due to a lack of pure culture studies. Here, we characterized the water-soluble and volatile breakdown products of 6:2 FTSA and 6:2 FTAB produced using Gordonia sp. strain NB4-1Y cultures over seven days under sulfur-limited conditions. After 168 h, 99.9% of 60 μM 6:2 FTSA was degraded into ten major breakdown products, with a mol% recovery of 88.2, while 70.4% of 60 μM 6:2 FTAB was degraded into ten major breakdown products, with a mol% recovery of 84.7. NB4-1Y uses two pathways for 6:2 FTSA metabolism, with 55 mol% of breakdown products assigned to a major pathway and <1.0 mol% assigned to a minor pathway. This work indicates that rapid transformation of 6:2 FTSA and 6:2 FTAB can be achieved under controlled conditions and improves the bacterial metabolism of these compounds.

Deep seepage of per- and polyfluoroalkyl substances through the soil of a firefighter training site and subsequent groundwater contamination

Per- and polyfluoroalkyl substances (PFASs) are utilized in specific firefighting foams. The objectives of this study were i) to map PFAS distribution in the soil and groundwater of a firefighter training site active for more than 3 decades, ii) to locate the main points of entry of PFASs into the aquifer and iii) to identify which PFASs seeped most deeply into the soil. A total of 44 soil cores and 17 groundwater samples were collected. Perfluorooctane sulfonate (PFOS), 6:2 fluorotelomer sulfonic acid (6:2 FTSA) and 6:2 Fluorotelomer sulfonamide alkylbetaine (6:2 FTAB) were the most predominant PFASs in surface soil. The highest total PFAS concentrations (up to 357 μg/g) were measured in two areas. Both areas were considered as potential points of entry of PFASs into the aquifer since PFASs were detected in soil 15 m below the surface, despite the presence of clay layers. The highest total PFAS concentrations were recorded in the monitoring wells located in the perimeter of the firefighter training site and in the spring located downgradient in the direction of groundwater flow. They ranged from 300 to 8300 ng/L. The fluorotelomer 6:2 FTAB was quantified in 6 monitoring wells, suggesting that this FT can reach a water table 20 m below the ground's surface.

Worldwide drinking water occurrence and levels of newly-identified perfluoroalkyl and polyfluoroalkyl substances

In the last decade or so, concerns have arisen with respect to the widespread occurrence of perfluoroalkyl acids (PFAAs) in the environment, food, drinking water, and humans. In this study, the occurrence and levels of a large range of perfluoroalkyl and polyfluoroalkyl substances (PFASs) were investigated in drinking water (bottled and tap water samples) from various locations around the world. Automated off-line solid phase extraction followed by ultra-high-performance liquid chromatography coupled to high-resolution mass spectrometry was used to analyze PFASs of various chain lengths and functional groups. In total, 29 target and 104 suspect-target PFASs were screened in drinking water samples (n=97) from Canada and other countries (Burkina Faso, Chile, Ivory Coast, France, Japan, Mexico, Norway, and the USA) in 2015-2016. Out of the 29 PFASs quantitatively analyzed, perfluorocarboxylates (PFCAs: C_4/14), perfluoroalkane sulfonates (PFSAs: C₄, C₆, C₈), and perfluoroalkyl acid precursors (e.g., 5:3 fluorotelomer carboxylate (5:3 FTCA)) were recurrently detected in drinking water samples (concentration range: <LOD to 39ngL^-1). Tap water samples from Canada showed noteworthy differences depending on their source; for instance, ∑₂₉PFASwas significantly greater in those produced from the Great Lakes/St. Lawrence River ecosystem than those produced from other types of sources (14 versus 5.3ngL^-1, respectively). A suspect-target screening approach indicated that other perfluoroalkane sulfonamides (FBSA, FHxSA), perfluoroethyl cyclohexane sulfonate (PFECHS), ultrashort chain (C₂-C₃) PFSAs (PFEtS, PFPrS), and two additional PFSAs (PFPeS (C₅) and PFHpS (C₇)) were repeatedly present in tap water samples (concentration ranges: <LOD to 4.0ngL^-1). To the authors' best knowledge, this constitutes the first observation of a cyclic perfluoroalkane sulfonate (PFECHS) and C₄-C₆ perfluoroalkane sulfonamides (FBSA, FHxSA) in drinking water. According to the newly updated US EPA health advisory for PFOS and PFOA (70ngL^-1), the drinking water samples collected in the present monitoring would not pose a health risk to consumers as regards PFAA levels.

6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB), a novel perfluorooctane sulfonate alternative, induced developmental toxicity in zebrafish embryos

6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB) is a major component of Forafac^®1157, a novel perfluorooctane sulfonate (PFOS) alternative used globally in aqueous film forming foams (AFFFs). Although 6:2 FTAB has been recently detected in the aquatic environment, its toxic effects on aquatic organisms remain unclear. Here, zebrafish embryos were exposed to various concentrations of 6:2 FTAB (0, 5, 10, 20, 40, 60, 80, and 100 mg/L) from 6 to 120 h post-fertilization (hpf) to investigate its developmental toxicity and possible mechanism of action. Results showed that exposure to 40 mg/L or higher concentrations of 6:2 FTAB significantly decreased the survival percentage and increased the malformation percentage. The median lethal concentration (LC₅₀) at 120 hpf was 43.73 ± 3.24 mg/L, and the corresponding benchmark dose lower limit (BMDL) of lethal effect was 33.79 mg/L. These values were both higher than those for PFOS, supporting the notion that 6:2 FTAB is less toxic than PFOS to zebrafish embryos. The most common developmental defect in 6:2 FTAB-treated embryos was rough-edged skin/fins. TUNEL assay showed that 6:2 FTAB exposure induced cell apoptosis in the tail region compared with that of the control, which might explain the rough-edged skin/fins. The increased transcriptional levels of p53, bax, and apaf1 and the increased activities of caspase-3, -8, and -9 provided further evidence of 6:2 FTAB-induced apoptosis. We also analyzed the effects of 6:2 FTAB on oxidative stress and the immune system. Results showed that reactive oxygen species and malondialdehyde accumulated in concentration-dependent manners after exposure to 6:2 FTAB, and antioxidant enzyme activities (catalase and glutathione peroxidase) also changed. Exposure to 6:2 FTAB also altered the transcriptional levels of ccl1, il-1β, il-8, tnfα, ifn, and cxcl-c1c, which play important roles in the innate immune system. Collectively, our data suggest that 6:2 FTAB exposure can induce cell apoptosis, oxidative stress, and immunotoxicity, thus highlighting the developmental toxicity of 6:2 FTAB in zebrafish embryos.

Certain Perfluoroalkyl and Polyfluoroalkyl Substances Associated with Aqueous Film Forming Foam Are Widespread in Canadian Surface Waters

The presence of perfluoroalkyl and polyfluoroalkyl substances (PFASs) commonly associated with aqueous film forming foams (AFFFs) at sites without known AFFF contamination is a largely unexplored area, which may reveal widespread environmental contaminants requiring further investigation. Sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) screening for 23 classes of PFASs, followed by quantitative analysis was used to investigate surface waters from rural, urban, and AFFF-impacted sites in Canada. The PFASs detected included perfluorohexane sulfonamide (FHxSA), 6:2 fluorotelomer sulfonamide (FTSAm), fluorotelomer sulfonamide alkylbetaines (FTABs), fluorotelomer betaines (FTBs), 6:2 fluorotelomer mercaptoalkylamido sulfonate sulfone (FTSAS-SO₂), 6:2 fluorotelomerthiohydroxyl ammonium sulfoxide (FTSHA-SO), 6:2 fluorotelomer sulfonamide alkylamine (FTAA) and C3 to C6 perfluoroalkane sulfonamido amphoterics. Detection of FHxSA in all urban and AFFF-impacted sites (0.04-19 ng/L) indicates the widespread presence of rarely considered perfluorohexanesulfonate (PFHxS) precursors in Canadian waters. FTABs and FTBs were especially abundant with up to 16-33 ng/L of 6:2 FTAB in urban and AFFF-impacted water suggesting it may have additional applications, while FTBs were only in AFFF-impacted sites (qualitative; ∑FTBs 80 ng/L). The distributions of PFASs moving downstream along the AFFF-impacted Welland River and between water and sediment suggested differences in the persistence of various AFFF components and enhanced sorption of long-chain fluorotelomer betaines. Total organofluorine combustion-ion chromatography (TOF-CIC) revealed that fluorotelomer betaines were a substantial portion of the organofluorine in some waters and 36-99.7% of the total organofluorine was not measured in the targeted analysis.

Influence of Environmental Factors on the Fate of Legacy and Emerging Per- and Polyfluoroalkyl Substances along the Salinity/Turbidity Gradient of a Macrotidal Estuary

This study aimed at bridging knowledge gaps regarding the land-sea transport of per- and polyfluoroalkyl substances (PFASs) through riverine discharge into coastal waters. The present survey was conducted in the Gironde estuary (southwestern France) where PFASs were ubiquitously detected albeit at low levels. Emerging PFASs such as fluorotelomer sulfonates or polyfluoroalkyl phosphate diesters accounted for a relatively minor proportion of ∑PFASs, while perfluorooctanesulfonate, perfluorohexanesulfonate, and perfluorohexanoate were the predominant congeners. Multiple linear regressions provided insights into the relative influence of factors controlling PFAS sediment levels. In that respect, the organic carbon fraction (strongly correlated to sediment grain size) appeared as a more important controlling factor than black carbon or distance from upstream sources for long-chain perfluoroalkyl acids. In the maximum turbidity zone (suspended solids up to 2600 mg L^-1), the particle-associated fraction was almost consistently >50% for long-chain perfluoroalkyl carboxylates and sulfonates (≥C8 and ≥ C6, respectively). Empirical models of K_D partitioning coefficients were derived by integrating, for the first time, both particle-concentration and salting-out effects. These results represent significant progress toward the development of numerical transport models integrating both PFAS partitioning and 3D-hydrosedimentary dynamics, with a view to estimate PFAS mass budgets at the land-sea interface.

Sorption of Fluorotelomer Sulfonates, Fluorotelomer Sulfonamido Betaines, and a Fluorotelomer Sulfonamido Amine in National Foam Aqueous Film-Forming Foam to Soil

During fire-fighter training, equipment testing, and emergency responses with aqueous film-forming foams (AFFFs), milligrams per liter concentrations of anionic, zwitterionic, and cationic per- and polyfluoroalkyl substances (PFASs) enter the environment. Because the behavior of zwitterionic and cationic PFASs in the subsurface is unknown, batch sorption experiments were conducted using National Foam AFFF, which contains anionic fluorotelomer sulfonates (FtSs), zwitterionic fluorotelomer sulfonamido betaines (FtSaBs), and cationic 6:2 fluorotelomer sulfonamido amine (FtSaAm). Sorption of the FtSs, FtSaBs, and 6:2 FtSaAm to six soils with varying organic carbon, effective cation-exchange capacity, and anion-exchange capacity was evaluated to determine sorption mechanisms. Due to the poor recovery of the FtSaBs and 6:2 FtSaAm with published PFAS soil extraction methods, a new soil extraction method was developed to achieve good (90-100%) recoveries. The 6:2 FtSaAm was depleted from the aqueous phase in all but one soil, which is attributed to electrostatic and hydrophobic interactions. Sorption of the FtSs was driven by hydrophobic interactions, while the FtSaBs behave more like cations that strongly associate with the solid phase relative to groundwater. Thus, the sorption mechanisms of the FtSs, FtSaBs, and 6:2 FtSaAm are more complex than expected and cannot be predicted by bulk soil properties.